...I had an FAA certified mechanic tell me recently that is was OK to fly a 212 with an inoperative hydraulic system because nowhere did it say in any maintenance publications that both hydraulic systems needed to be operative for flight. I just looked at him and, without trying to laugh too much, said it needed to be fixed and he got angry and demanded me to prove my point. To which I said, it ain't going anywhere until you fix it. Then he wanted to punch me in the nose.
My philosophy is if it's fitted to the aircraft it needs to be operative, unless the MMEL says otherwise. And whatever the MMEL says, or doesn't say, it always remains the prerogative of the pilot to require a defect to be rectified even if the MEL provides a waiver in the circumstances.